Roofs of the vehicles generally include a skeleton frame and a roof panel formed from a sheet metal and attached to the skeleton frame. One example of known vehicle roof structures is shown in Japanese Patent Laid-open Publication (JP-A) No. 2005-153649.
The disclosed vehicle roof structure, as shown in FIG. 13 hereof, includes a side roof rail 202, a center roof rail 203 and a roof panel 205 joined together by spot welding. The side roof rail 202 and the center roof rail 203 have a closed cross-sectional configuration to improve the stiffness of the vehicle body against a side or lateral collision. The center roof rail 203 of closed cross-sectional configuration has a first access hole 204 to allow access of a welding electrode (not shown) to a weld spot when the center roof rail 203 and the side roof rail 202 are to be welded together. Similarly, the side roof rail 202 of closed cross-sectional configuration has a second access hole 206 to allow access of another welding electrode (not shown) to a weld spot when the roof panel 205, the center roof rail 203 and the side roof rail 202 are to be welded together.
The vehicle roof structure 201 of the foregoing construction is not fully satisfactory in that the access holes 204, 206 lower the strength of the vehicle roof structure 201.
It is accordingly an object of the present invention to provide a vehicle upper body structure, which has relatively high stiffness and strength, and is able to insure stable one-sided spot welding operation with less variation in the welded position.